1. Field of the Invention
The present invention relates to an apparatus for anchoring surgical suture to bone. More specifically, the present invention relates to a suture anchor having apertures at the distal tip thereof for anchoring sutures in the cortical bone during arthroscopic surgery.
2. Description of the Related Art
When soft tissue tears away from bone, re-attachment becomes necessary. Various devices, including sutures, screws, staples, wedges, and plugs have been used in the prior art to secure soft tissue to bone.
Recently, various types of threaded suture anchors have been developed for this purpose. Some threaded suture anchors are designed to be inserted into a pre-drilled hole. Other suture anchors are self-tapping.
U.S. Pat. No. 5,156,616, for example, discloses a suture anchor which has an axial passageway extending through the suture anchor. The passageway has a proximal portion, a central portion, and a distal portion. The proximal portion is hexagonally-shaped to cooperate with a hex driver for installing the anchor. The distal portion is sized to receive a knotted piece of suture, and the central portion has a diameter less than the that of the proximal and distal portions to receive the suture being threaded therethrough. Use of the suture anchor disclosed in the '616 patent, however, requires tying a suture knot. If the knot is not tied securely or if the knot is not made large enough, there is a risk that the knot will unravel or be pulled through the distal portion of the passageway.
Another prior art suture anchor is disclosed in U.S. Pat. No. 5,370,662 and has an eyelet located on the proximal end of the anchor through which a suture can be passed. Since the eyelet is formed as part of the drive head, however, combining these two functions in one structure often tends to weaken the drive head.
Problems can arise if the structure for attaching the suture fails, allowing the suture to become detached from the anchor. For example, if the suture anchor is biodegradable, the eyelet can degrade rapidly, causing the suture to become detached from the anchor prematurely.
Further, such a prior art suture anchor having an eyelet extending from the proximal end thereof requires countersinking of the eyelet below the bone surface to avoid having the patient's tissue abrade against the exposed eyelet. As a result, suture attached to the eyelet is vulnerable to abrasion by the bony rim of the countersunk hole into which the suture anchor is installed.
In addition, various other modifications to the drive head often are employed in connection with suture attachment. For example, recessed grooves may be formed on opposite sides of the drive head to receive and protect the suture from abrasive areas of the suture anchor tunnel or to facilitate mating between the anchor to the driver. In such cases, the drive head often must be made of a larger diameter to recover the mechanical strength lost from the removal of material relating to the suture-attachment or suture-protection modifications.
Accordingly, a need exists for a threaded suture anchor to which suture is secured effectively so as to prevent detachment of the suture. In addition, a need exists for suture anchors that will not abrade tissue and do not require countersinking.